Transparent pyroxylin plastic composition



no STATES PATENT Frrcn.

JOHN H. STEVENS, OF NEWARK, NEW JERSEY, ASSIGNOR TO THE CELLU- LOID COMPANY, OF NEW YORK, N. Y., A CORPORATION OF NEW JERSEY.

TRANSPARENT PYROXYLIN PLASTIC COMPOSITION.

SPECIFICATION forming part of Letters Patent No. 622,290, dated April 4, 1899. I Application filed December 20, 1898. Serial No. 699,839. (No specimens.)

T0 to whom it may concern.-

Be itknown that I, JOHN H. STEVENS, of the city of Newark, county of Essex, and State of New Jersey, have invented certain new and useful Improvements in Transparent Pyroxylin Plastic Compositions, of which improvements the following is a specification.

My compositions are intended principally for use in the arts as imitations of amber, glass, and tortoise-shell. I have found by a long experience that the essential character-.

istics for such imitations are solidity, transparency, plasticity under heat or capability of being pressed into different shapes in hot dies or otherwise when in a hard condition, and permanency or resistance to the action of time or elevated temperatures.

\Vhile the different ingredients from which 1 form my compositions are well known and at least one of them has been used or suggested to be used in connection with pyroxylin, they have not, so far as I am aware, been brought into the peculiar new relations which I have demonstrated form a composition possessing entirely new properties of great value in this art. The property of permanency in these transparent compounds is of extraordinary importance, because it is closely associated with the danger of destructive fires and deterioration of valuable goods.

There are plenty of known means for securing stability in non-transparents or even in clouded transparents; but the arts demand a high transparency in order to successfully imitate amber and glass effects, and it has been extremely difficult to secure high transparency and stability at the same time. Hence any composition of matter which gives the desired properties has to depend on study and experiment, especially with proportions, the properties of substances, and their behavior under special conditions of manufacture, such as their reaction or compatibility with other necessary ingredients of the transparent compounds.

It frequently happens, as I have already pointed out in my United States Patent No. 519,987, that the mere employment of a substance in connection with pyroxylin does not necessarily disclose its usefulness or the peculiar properties which it may give the compound under various conditions of treatment or in various combinations. This is illustrated in the history of the art. Pyroxylin (which is a product of the action of nitric and sulfuric acids on cellulose either in the form ofcotton or paper) is by reason of its solubility in various menstrua a basis for a large variety of compounds Whose applications are almost nnmberless. It is because of these many applications and the peculiar properties demanded for their many uses that inventors have given them so much attention. Many hundreds of patents have been issued both in this country and abroad for various processes, mixtures, and applications in this art. First, the pyroxylin itself has been made by many processes and subjected to various treatments; second, the compounds have been made by numerous special processes; third, liquid solvents in great variety have been discovered and applied; fourth, solid solvents or solvents which when melted by heat or dissolved in a liquid act on the pyroxylin have been discovered and used in great variety;

fifth, various non-solvent substances have been used tomodify the character of the compounds and render them susceptible of special application; sixth, special combinations or the association of old ingredients with new processes have advanced the art, and such is the peculiar nature ofpyrexy-lin and its compounds that these special combinations of known ingredients and their uses with special processes have formed one of the most important fields for improvement, and, seventh, the applicability of special compounds to particular uses has formed the basis for numerous inventions.

The present invention is based on the discovo eryof certain newpropertiesin solid bodies not necessarily in themselves solvents of pyroxylin, and also in their action with other ingredients and the necessary proportions to be used, and its place in this field is best under- 5 stood by referring to the history of a somewhat similar line of invention. Thus by some inventors certain inorganic salts have been proposed to be used to render pyroxylin compounds non-infiammable. Examples of such we salts, for instance, are chlorid of calcium, chlorid of zinc, 85.0.; but in order to effect such result they must necessarily be used in large proportions to the amount of pyroxylin present. So, also, some other, salts, such as chlorate 0t potash and nitrate of soda, have been added by some inventors to the explosive varieties of nitrocellulose in order to increase the explosive power. Still, again, certain salts have been proposed to be used when added to non-solvents of pyroxylin, like ethyl alcohol, in order to make the mixture a solvent of pyroxylin; but none of these uses is in any way analogous to my invention, which relates solely to the discovery that certain salts when added to pyroxylin compounds in certain proportions have the effect of neutralizing the nitrous acid developed in such compounds, and thereby tend to preserve these compounds from deterioration, while at the same time they do not interfere with the transparency of the compound, which is so desirable for many purposes. That the discovery of the utility of the salts mentioned in this specification for this purpose is foreign to the various inventions of prior inventors recited above is shown by the fact that many of the inorganic salts and equiva lent substances referred to by them as useful for the several purposes above mentioned are wholly unsuited to the purposes of my invention.

The salts that I refer to and which are included within my invention are known as the sodium salts of the volatile monatomie fatty acids. The principal acids of this group are formic, acetic, propionic, butyric, and Valerie acids. The salts resulting from the chemical combination of these acids with ,sodium are sodium fol-mate, sodium acetate, sodiu m propionate,sodiu m butyrate,and sodium valerate. These are the salts which form one part of my new transparent composition of matter, consisting, essentially, of pyroxylin, camphor, a liquid solvent, and an antacid or preserving substance, and of these salts I prefer sodium acetate. I have used these salts successfully and have determined by experiment their relative value for the purpose. \Vhile they all possess more or less antacid power, I prefer to use the salts which are most easily soluble, especially in alcohol or wood spirit, because these are the solvents most commonly used in the art. lVhile an ordinary mechanical mixture of the preserving agent with the pyroxylin compounds is sufficient to impart stability, the employment of a solution of the salt permits a better distribution, so that every part of the pyroxylin compound is protected by reason of intimate contact with the salt.

In making my new composition I mix soluble pyroxylin with a liquid solvent and sufficicnt camphor to give the final product molding properties. The liquid solvent is preferably wood-alcohol and is used in suffieient proportion to produce a mass which can be masticated in the rollers or mixing machinery, although I do not confine myself to any particular proportion so long as the final result is a solid transparent compound. I introduce the antacid salt preferably in solution in woodspirit, although it can be introduced in the form of powder, in which case themastication with the solvent and other ingredients results in a thorough incorporation of the salt. The well-known menstruum (acetate of methyl) can be used in place of wood-spirit, if desired, or, in fact, any good solvent which will dissolve the antacid salt or permit it to become incorporated with the pyroxylin. As to proportions I find that one per cent. of the salt, by weight, to the pyroxylin is sufficient for good results, while not more than three per cent. should be used. I have discovered in operating with these salts that those which dissolve most readily in the solvent used to form the compounds are the most powerful in their preserving effects. The formate of sodium is more feeble in antacid power than the acetate and is less easily soluble and gives only a moderate transparency.

I would recommend that the formate of sodium be confined to products in which high transparency is not specially desired and which are not to be subjected to severe con-.

ditions of treatment, like heat, for instance. Nevertheless it is a fair antacid.

The propionate and valerate of sodium are as powerful as the acetate, but the butyrate is also a strong antacid. The butyrate and valerate have a more or less offensive odor. All of these salts with the exception of the formate seem to be, proportion for proportion, superior to urea as preservers. While the products made with them are more inclined to yellowness than urea-pyroxylin compounds, they possess the elements of efficiency and cheapness. They possess other advantages over some of the antacids heretofore used. For instance, pyroxylin compounds made with urea are sometimes contaminated by a product resulting from the reaction between the urea and the nitro elements present. This product is presumably nitrate of urea. At any rate compounds made with urea when subjected to severe treatment, like heat in contact with metal plates, are liable to a smearing of the surface of the sheets and a staining or smutching of the polishing-plates 01' metal dies. In using these sodium salts, especially those stated to be preferred, like sodium acetate, this does not occur, and imitation tortoise-shell sheets, for instance, made with sodium acetate as the preserving agent,present abetter surface and the polishing-plates last longer than is the case with urea compounds.

The art of manufacturing transparent py roxylin compositions is well known, as is also the difficulty which the operators have experienced in making these compositions so that they would be unchangeable by time or the influence of elevated temperatures, such as are used in molding. Many antacid substances have been usedfor this purpose; but

as a rule they have failed to give the requisite transparency, either bylack of solub l-. ity inthe menstrua employed or non-compatibility in other respects.

\Vhile Ionly confine myself to the proportions and ingredients necessary to produce solid transparent compositions, I would state that good proportions are, by weight, one hundred parts of soluble pyroxylin, forty to fifty parts of camphor, fifty to seventy-five parts of wood-spirit, and one part of sodium acetate. I have discovered that solvents in which the sodium acetate is insoluble can be used with the compound, provided the antacid salt is first dissolved in wood-spirit. I have also discovered that cam phor, which by itself is incompatible with these sodium salts, is entirely compatible with them when used as described. There is no separation nor consequent cloudiness which would be fatal to the effect desired. I prefer, the roll method of conversion.

I confine myself to using no more than three per cent. of the sodium salt to the amount of pyroxylin. More than this would make a compound unsuited for my purpose, as it would either lack the requisite transparency or possess other undesirable properties. For instance, I find that five per cent. of the sodium acetate to the pyroxylin gives my mixtures a decided brown color, which unfits the compound for useful transparent effects. As a rule I would recommend the use of one per cent. of the antacid salt as a good general proportion, especially as one per cent. gives paler effects and better transparency than larger proportions; but I have successfully used less than one per cent. in cases where a high stability was not required. I find also that when the top limit of three per cent. is reached the sodium salt and the other salts of this class begin to have a decomposing tendency on the pyroxylin, especially under the influence of heat, so that in such excessive proportions they do notindicate the preserving action which they possess when used in about one per cent. proportion. WVhat little transparency is possessed by excessive proportions disappears and the products turn clouded, become brittle, and stain the polishing-plates when heated.

As regards the effect of proportion on the transparency I find that, considering formate as the first of a series consisting of formate, acetate, propionate, but-yrate, and valerate, the ability -to hold transparency with larger proportions-say two per cent. and upward-- increases gradually as we rise in the series. The formate, for instance, is perceptibly clouded at two per cent, while the valerate at two per cent. is still highly transparent.

\Vhile I am unable to explain why a basic substance already saturated with an acid can act as a preserving agent and prevent the deleterious action of the corrosive nitro com pounds in decomposing pyroxylin, my experiments have nevertheless demonstrated this to be a fact. I can only state that it seems to depend on the nature of the acid radical present in the preserving agent. Even when the elements contained in these preserving salts are united to other substancesfor instance, in neutral salts containing dissimilar acid radicals-the resultant compound salt possesses preserving power at least in proportion approximating to the amount of such element present. As an instance of the effect of the nature of the acid radical present in the preserving-salts, I can state that while I have found by experiment that sodium acetate is a good antacid substance in connection with pyroxylin sodium phosphate has so little antacid power in it that my tests have failed to disclose it, and at any rate can be considered as totally inefficient as an antacid for my compositions. Very often a substance dissolves in wood-spirit and forms a close highlytransparent combination with the pyroxylin compounds, while it is of no use for antacid purposes. In fact, hygroscopicsubstances, as some of the chlorids for instance, chlorid of calcium-while they may be capable, in connection with alcohol, of making a celluloid useful for artificial silk, filaments for lamps, and a certain class of varnishes, are totallyincapable of forming a useful imitation of amber, tortoise-shell, or glass having the requisite surface effects. I have long known by experience that chloridof-calcium compounds attract moisture and become wet on the surface, which property would prevent the sale of such articles as tortoise-shell combs, amber pipe-bits, or transparent sheets for decorative purposes, for all of which my invention is especially applicable.

While the solution of chlorid of calcium on the surface can be Washed away to some extent, it is always liable to exude from the body of the material and form fresh deposits. Such materials are either incapable of polish or will not retain their polish by reason of this exudation.

I am aware that sodium carbonate has been used as an antacid in pyroxylin compounds. In this case the theory is that the sodium is combined with a non-corrosive and harmless acid radical, which when released immediately passes off in the gaseous state. The pyroxylin products made with carbonate of sodium are not as transparent as those made with acetate of sodium and the preserving power of the acetate is higher. Its penetrating power also gives it superiority over the carbonate. The carbonate of sodium is quite distinct also by reason of its insolubility in alcoholic menstrua.

By solid transparent pyroxylin compounds I mean those which permit the transmission of light-for instance, sheets, rods, or articles madeinimitation of amber, glass, tortoise-shell', and horn.

I am aware that the sodium acetate has been claimed as a solvent in connection with grainalcohol in any proportion and as a substitute and equivalent for calcium ehlorid and other chlorids of the metals and alkaline earths, as well as oxalic, citric, and carbolie acids. I understand by any proportion an y proportion which will enable it to dissolve the pyroxylin, such proportion being at least five per cent. to the amount of alcohol used and the alcoholic solvent to be employed unmixed with and as a substitute for other solvents and in sufficient quantity to dissolve the pyroxylin. There has been suggested as an economical proportion three parts, by weight, of alcohol to one part of pyroxylin. My experiments have demonstrated that all proportions in which it has been recommended to be used would fail to give a final transparent composition of matter. I am not aware, therefore, that the acetate of sodium has ever been used in making a plastic or moldable imitation of glass, horn, amber, and tortoiseshell or that it has been used in such proportions as would form such a composition or that any one before my experiments and the reduction to practice of this invention has known or described the valuable property of sodium acetate in mycompounds or has even suggested its utility with camphor or other solvents outside of the alcohols.

\Vhile I have found that sodium acetate and the rest of my new group are applicable as antacids for purposes outside of the transparent pyroxylin compounds of the present invention-for instance, smokeless powders and lacquersnevertheless as there are other suitable antacid substances useful for non-transparent compounds and because of the extraordinary utility of these new antacid substances in solid transparent moldable compounds I have confined my claims to this class of compounds.

lVherever I have mentioned camphor, it is to be understood that I can employ any equivalent solid solvent which will give the compound the molding property or the property of plasticity under heat, as is well understood. Many such substances are known. I

do not, therefore, claim the broad use of these new antacid substances with pyroxylin in .all proportions; but I include in my invention any use of my proportions of sodium acetate or the rest of the group in a solid transparent camphor compound as a practice of my invention, whether the compound is made as I have described or by adding to an ordinary transparent camphor com pound su fficient alcohol and acetate of sodium to give my proportions and results; for I have found that the usefulness of the acetate of sodium as an antacid in my compounds was unknown in the art until I made my invention.

For the reasons above described I include in myinvention the present group of sodium salts of the volatile monatonlic fatty acids as preserving agents for transparent pyroxylin compounds, whether the salts are simple, compound, mixed, or combined chemically with other salts or compounds; but Iexclude any combination of the salts of this specification with the halogen acids, for such compounds have already been secured by me in United States Patent No. 614,514, of November 22, 1803, which patent includes such substances, for instance, as chlorformate of sodium, chloracetate of sodium, chlorpropionate of sodium, &e.

Having thus fully described my invention, what I claim, and desire to secure by Letters Patent, is-

1. A solid transparent composition of matter consisting of pyroxylin, camphor, a liquid solvent,and a preservingsodiu in salt of a volatile monatomic fatty acid, the said salt being present to no greater extent than three per cent. by weight to the amount of pyroxylin in the compound, substantially as described.

2. A solid transparent composition of matter consisting of pyroxylin, camphor, and a preserving sodium salt of a volatile monatomic fatty acid, the said salt being present to no greater extent than three per cent. by weight to the amount of pyroxylin in the compound, substantially as described.

3. A transparent composition of matter containing pyroxylin, camphor and sodium acetate, the said salt being present to no greater extent than three per cent. by weight to the amount of pyroxylin in the compound, substantiall y as described.

JOHN II. STEVENS. lVitncsses:

ABRAHAM MANNERS, RALPH RooKsLEY. 

